Amplifying and reproducing system



Jan. 1, 1935. B. F. MIESSNER AMPLIFYING AND HEPRODUCING SYSTEM Filed Jan. 25, 1929 2 Sheets-Sheet 1 ahmmtoz W T N E5 5 Jan. 1, 1935. B. F. MIESSNER ,9

AMPLIFYING AND REPRODUCING SYSTEM Filed Jan. 25, 1929 2 Shets-Sheet 2 o'o'onun INVENTOR BENJAMIN F. MIES SNER ATTORNEY Patented Jan. I 1935 I v V T f' nemoneomo SYSTEMF' Benmfialvfiessnenflhort Hi1ls,' N.1J-.; assignorf assignments, tmRadiotGorporation of g l America, New Yonk,,.N.. Y1. ,a; corporation of Delaware j epplii;new 25, 1929, LSeriall K012334371 H H 1 emmas, 101.119; 17 1;);v V p p The present invention-relatestbamp1ifying terminal-*being*"shown grounded: The plate and reproducingsystems; and particularly such potential for 'tube,VT1 is indicated' asreduced systems employing three electrode vacuum tubes through-Ipassingthe current through series reand-energized"reproducing devices'. V I sista'nce'R'a and further filtered wit-h"the-aidfof' 5 A particular object istoenergiz'ethevacuu'm condenserCzw Potentiometers 'Ki 'andpro 5 tubes and the-field or the reproducing-- devicein vide for conhe'ctionsofthe filaments offthtubes a system from a source -of-' uni-directional togroundthrough'gridbias producingresistances-- fiuotuating cur-rent while maintainin'ghumpro Riand Rz-r espectivelyi' Condenser Cristasignalduction in-the reproducingdevice low. current by-pass around resistance R1. The' Another'object is-toavoidthe-use -of an-ex-' features so -far mentioned are -usual togeneral 0 i cessive amount of the bulky-and heavy apparatusj practicefand-requir e no detailed explanationa usual to filter systems -employed in cormection" The-itwo sections Ps" 'andPf ofythe push=pull with the energizing of vacuum-tubes fromum outputtranstormer- T3 are shown -connected' steady sources of eleetrical energy; 3 througharesistanoe R4 t o'whichthe positiveside" The'features-of my inventi'om are described of the; filter output is connected through 5" withitheaid QfEthe figures 'of the accompanying variable contact E to energize-the plate circuits drawings in whichlikereflerenoe characters of tubes V'l' .andVT2"",'an arrangementfil repre'sent like elements so far ass possible in the of particular value in an amplifying systemhav I several figures; ing a push-pulllstage oi 'amplifioationwhen =the- Fig. '1 diagrammaticallyi1lustratesan amplisystem is energized f-rorrran' alternating current- 20 T fying and reproducing systmsi'ncludi ngwthe Suppl-ya If the two sides -of -a-push-pullamplifier features of myinvention; Fige 2 sh'ows amodifie'd are-nicely' balanced throughout the arrangement form of a: feature'of- 'my invention in the-ampli-- will automatically neutralize hum producing" fyingzportion of the system Fig. 3 shows: any effects resulting from energizing the tubes' ffom" other modification of the feature of Fi'gi 2 2 Fig; air-alternating current source; which would be a 2 4 illustrates thesystem shownin Fig. 2 irhcon desirable feature it- 'th'e one push pull istage ot nection with a more complete' circuit; amplification were the only-= stage in: -use,-' but ReferringtoF'ig:Lacascadeconnected amplimult'i-stage"amplification it is often most de fier is shown to inelude athree electrode vacuum' sirableto-havesome "hum producingcurrent in tube VT1 coupled through transformer T2 to-a the push-pull stage-to neutralize-hum producing-v30" pair of three electrode-'tubes-vTz and-'VTz'- concurrents that'come f-rom one-or m'ore preceding nected in push pull relation in'well -knowm man-- stages; or it may be desirable to have a residual ner; Transformer iTi provides-an input forcurhum producin'g currentinfthepush -mull stage-to rents torbe'amplified totube vTn'andltransformert pass onward; for aparticular: use, such-1 as; v

Talprovides -an outputQto-a reproducing-device neutralizing current im a, succeedingi repro 5 later described; I 1 'duoingdevice which humproducing current may A transformer T- having a primaryP'ir-icluded well -existin some forms oi reproducin'g devicesinilanl alternatingicurrent supply systenr-has' a-'-' used i-ii-particulariways; as the so call'ed rdynami'csecondary? S1 for supplying heating current-to": loadj speaker having its fielrl coil energized by" I 40 the filament of tube M VT1, T a secondary I S2 for current coming from the so'urce usecr'fomenergiz 0" supplyingr heating current to the-' filaments of ing'thetubes of theamplifierzi Iishowlini Fig. 1' tubes VTz and VTi; a secondary Sa for'heating and will 1 describe later th'ecuse ofi ac dynamic the filament of a rectifiertuberlFt ih and a secspeaken involving suchi a-neutralizing effect; ondary S4 for supplying alternatin'g cunrent itd In general thecommercial productioniofctubes the anodes 'of rectifier tube -Ri'I' for rectificationand devices fonma'king' upfiaApush-pullstagei0fi andsupply to:the pl'atemircuits ofi the amplifier-1? amplification, and usual means for energizing; v tubes bywayof thefilter system including con the: tubes; donotjperm'it ofisassemblinga'awithany densers' C3 and Cy and coil Fcj the -positi ve and hope of having'the.systentbalancedifornhum elims' negative=terminals :.of the -filter output being :asi. ination', or unbalanced inamtldesired way; andi'ttz:

5 indicated by the conventional si'gns, lthennegativei maybe thatJany haphazardounb'alance iohtain'etlii P a one way or the other I can overcome any hum unbalance in the push-pull system, or can generate any degree and phase of hum in the pushpull system to neutralize hum coming from tube VTl, or the residual of hum in aplu'rality of preceding tubes. In addition it is possible to have from the neutralizing of hum as between the push-pull stage and preceding stages a residual of desired phase to pass onwardto a reproducing device, or for other use, if desirable. I

. I show a dynamic speaker having-a field'coil FC connected in the filter circuit in orderto utilize the rectified current thereof for energizing the field, and at the same time employ theinductive effect of this field winding usefully fo'rfllr... tration purposes, thus avoiding the use of sep-.

arate means for energizing the field coil and chin heating the use of one or more filter choke coils usual in filter systems.

I show the usual movable coil MC mechanically associated with a conical or other suitable sound producing element G of dynamic speaker practice, the movable coil being in the field of ,the core of field coil FC. The movable coil MC is connected in circuit with the secondary of output transformer T3. 7 I

Because field coil FC is energized from the same unidirectional fluctuating current that energizes the tubes the effect of its fluctuating field on movable coil MC can be opposed by residual.

fluctuations of proper phase from the push-pull stage passing through coil- MC. However, in View,v of the small number of turns in the coil MC inusual dynamic speaker construction it is diificult to create enough fluctuating field in coil MC to adequately oppose the fluctuating field of field coil FC, and in such cases an additional bucking or neutralizing coil NC wound on the core of the field coil and connected, in series with the mov-;

able coil is of great help in accomplishing the desired result.

Of course transformers T2 and T3 can be poled as may be required to aid in arriving at phase conditions favorable to the neutralizing effects I have described; however, this is not in itself a specific feature of the present invention, I having utilized this feature in systems described and claimed in patent applications heretofore filed by me.

In Fig. 2 I show how the hum conditions in the push-pull stage can be determined and controlled in a way different from that in Fig. 1. case I provide separate connections from the two sections of the secondary of push-pull transformer T2 to the grid bias producing resistance R2 through adjustable contacts E and E". Since the fluctuating current flows through resistance R2 it is possible by selecting proper points of contact thereon to introduce any desired unbalancing effects in the push-pull stage, so that such an arrangement can be inserted in Fig. 1,.as the equivalent of the push-pull arrangement shown therein. I s l 'Fig. 4 which shows the same type of push-pull circuit as Fig. 2 illustrates the connection of the said tubes to saidpotential developing element system toa power supply device and also to a utilizing circuit. The input of the push-pull are;

In this rangement in Fig. 4 is coupled to the output of a tube VT1 through a transformer T2.

Fig. 3 shows another arrangement for determining and controlling the hum producing characteristics of a push-pull stage of amplification. I show variable resistances R5 and R6 in the plate circuits of tubes VT2' and VTz" in lieu of the adjustable resistance R4. in Fig. 1, and adjustment of these resistances permits of determining and controlling the hum producing current and phase of it in the push-pull stage. In some constructions one of these resistances may suflice for securing theadjustment desired.

If it is-"needed to moderate feed back coupling between the grid and plate circuits in the grid bias producing resistance of the push-pull stage the provision. for avoiding this shown in Fig. 3

"ter including a high resistance R7 and a con- .denser'Csof adequate capacity to by-pass signal current direct to the filament from the grid circuits. Having: described 'my'invention I claim:

1. In an amplifier system, the combination of a pair ofelectron discharge tubes including grid, filament and plate circuits, means for energizing the filaments of said tubes in parallel with alternating current, push-pull input and output devices therefor connected respectively in the gridfilament and plate-filament circuits of said tubes,

an impedance common to saidgrid-filament and plate-filament circuits for developing a gridbias potential, and connections between said input devices and saidimpedance for regulating the space current of said tubes whereby the fluctuations in the output current of one of said tubes may. be made to neutralize the fluctuations in the output current of the other of said tubes.

2. In an amplifier, a pair of multi-electrode tubes, means for energizing thecathodes of said tubes with alternating current, said tubes having their input and output circuits connected in push pull relation, a grid biasing resistor means common to the grid-cathode circuits of said tubes, and a variable connection from the grid of each tube to said biasing means.

3. In an amplifier, a pair of multi-electrode tubes, means for energizing the cathodes of said tubes, said tubes having their input and output circuits connected in push pull relation, a grid biasing resistor means common to the gridcathode circuits of said tubes, and an adjustable tap from the grid of each tube to said biasing means, said taps being independent of each other.

4. In an amplifier system the combination of a pair of electronictubes each thereof including anode, cathode and grid electrodes push-pull input and output circuits therefor, a source of energy to be amplified said energy having superimposedthereon an undesired hum component, means for coupling said source to said push-pull input circuit said means acting to impress upon said push-pull input circuit the energy desired to be amplified. together with the superimposed undesired hum component, a translating device, means for coupling the push-pull output circuit to said-translating device, said push-pull output circuit including ananodc return circuit common to both said tubes comprising a potential 1developing elementand a source of uni-directional fluctuating current in series, means for connecting the grid; input electrodes of both of for. imparting a grid biasingpotential' to both the phaseand imagniturl'e: or the' -gridf biasing potential fluctuating ?c omponent so that it op transferredt:to the push pull inputcircuitto any desired degree. 5. In an amplifiersystem the combination of a,

pairllofLelctron-ic 'tubeseach thereof including anode, cathode and grid electrodes, push-pull input and output circuits therefor, a ,source of energy to be amplified, said energy having superimposed thereon an undesired humcomponent, means for coupling said source to said push-pull input circuit, said means acting to impress upon said push-pull input circuit. the energy desired to be amplified together withthe superimposed undesired hum' component, a translating device, means for coupling the push-pull output circuit to said translating device, saidpush-pull output circuit including a common anode return circuit comprising a potential developing element and a source of uni-directional fluctuating current in series, means for connecting the grid input electrodes of both of said electronic tubes to said potential developing element for imparting a grid biasing potential to both of said tubes,*said grid biasing potential including a fluctuating compon ent derived from said source of fluctuating current and means for controlling the phase and magnitude of the grid biasing potential fluctuating component so that its effect upon said tubes when combined with the effect of the undesired hum component transferred to the push-pull input circuit produces in the push-pull output, a fluctuating current component of predetermined phase and amplitude.

6. In an amplifier system, an electronic relay, input and output circuits therefor, a pair of electronic tubes, push-pull input and output circuits for said tubes, a source of uni-directional fluctuating current connected to the anode circuits of both the electronic relay and the push-pull connected tubes to furnish anode current for the same whereby there exists in the output circuits of both said relay and push-pull connected tubes a fluctuating current component derived from said source, means for coupling the output circuit of said relay to said push-pull input circuit said means acting to transfer fluctuating current components present in the output of said electronic relay to said push-pull input circuit, a potential developing element in said push-pull output circuit forming a series circuit with said source of current whereby current flowing in the push-pull output circuit of said tubes passes through said potential developing. element, means for supplying biasing potentials to both said push-pull connected tubes comprising means for including at least a portion of said element in said push-pull input circuit whereby there is impressed upon the push-pull input circuit the effect of atleast a portionof the fluctuating current component from said source and means for adjusting the magnitude and phase of said impressed fluctuating current component to oppose to any desired degree the effects of the fluctuating current component transferred to said pushpull input circuit through said coupling means.

7. In an amplifier system the combination of a pair of electronic tubes, push-pull input and output circuits therefor, a source of energy to be amplified including an undesired hum component,

noes- 94 substantially neutralized.

nieans for coupling said source: to said =-.pu-sli-pull': input circuit; :sai'd means acting to impress upon said"- push -pull :input circuit not: fonly the i energy desire'dtobe-amplifled but-also the undesiredi'hum component,laltranslatingvdevice, means for cowpling;,-'the'push pul1 outputz'circuit to" said trans latingi device;.-a: common: filamentv energi'zingisys tem for both said tubes includin'gra' source of V alternating current; the filaments iof isaid tubes being ccnnectediirii parallel relative tu saidisourc'e' of alternating current, an impedance effectively across said source of alternating current and said filaments, a common plate return connection from the center of said push-pull output circuit to a point of said impedance said connection includ-- ing a potential developing element and a source of uni-directional fluctuating current in series ponent so that its effect upon said tubes is combined with the effect of the undesired hum component transferred to said push-pull input circuit to produce in the-push-pull output circuit a fluctuating current component of predetermined phase I and amplitude;

8. In an amplifier system the combination of a pair of electronic tubes each thereof including anode; cathode and grid electrodes, push-pull input and output circuits therefor, a source of energy to be amplified the energy to be amplified having superimposed thereon an'undesired hum component, means for coupling said source to said push-pull input circuit said means acting to impress upon the push-pull input circuit the energy desired to be amplified together with the superimposed undesired hum component, a translating device of the type utilizing a field winding, means for energizing said field windingcomprising a source of uni-directional fluctuating current, means for coupling the push-pull output circuit to said translating device said push-pull output circuit including a common anode return circuit comprising a potential developing element and said source of uni-directional fluctuating current r in series, means for connecting the. grid input electrodes of both of said electronic tubes to said potential developing element for imparting a grid biasing potential to both of said tubes, said grid biasing potential and said translating device field including a fluctuating component derived from said s'ourceo-f fluctuating current, means'for controlling the phase and magnitude of the fluctuating current component impressed upon said thermionic tubes so that its effect when combined with the effect of the undesired hum component transferred to said push-pull input circuit produces in the push-pull output a fluctuating currentcomponent of predetermined phase and amplitude, the effects of said last named fluctuating current component being transferred to said translating device through said coupling between the push-pull output circuit and the translating device whereby the effects of the fluctuating cur- I rent component inthe field of said translating device due to the energization thereof from'said source of uni-directional fluctuating current is 9. In an amplifier a pair of multi-electrode electronic tubes, means for energizing the cathodes of said tubes with alternating current, push-pull input and output circuits for said tubes, a' poten-' tial developing element common to the grid cathode circuits of said tubes, a variable connection from the grid of each tube to said biasing means and a common anode return circuit including said grid biasing means'and a source of uni-directional fluctuating current.

10. In an amplifier circuit a. pair of multi-elec 10 trode electronic tubes, means-for energizingthe BENJAMIN F. MIESSNER. 

